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Biomedical subjects

T Sakai

Publications and source records attributed to T Sakai.

At least 235 records · Page 13Linked to original sources
PubMed2000

High plasma cardiac natriuretic peptides associated with enhanced cyclic guanosine monophosphate production in preascitic cirrhosis.

BACKGROUND/AIMS: The initial abnormalities of renal sodium handling in cirrhosis remain unclear. The aim of this study was to characterize sodium metabolism in preascitic cirrhosis. METHODS: Ten patients with preascitic cirrhosis and ten controls were studied. All subjects ate a diet providing 120 mmol sodium during an equilibration period lasting 5 days and the study day. On the study day, after remaining in bed, plasma levels of atrial natriuretic peptide, brain natriuretic peptide, renin activity, aldosterone, noradrenaline, and cyclic guanosine monophosphate were measured at 7 am. Thereafter, they were instructed to maintain an upright posture until dinner and the measurements were repeated at 9 am and 6 pm. After having dinner, all subjects were asked to remain in bed and the measurements were repeated at 11 pm. To measure renal sodium and cyclic guanosine monophosphate excretion, 24-h urine collections were performed, starting from 7 pm on the day before the experimental day. RESULTS: Plasma levels of atrial natriuretic peptide, brain natriuretic peptide and cyclic guanosine monophosphate in patients with preascitic cirrhosis were significantly elevated compared with those in controls at every sampling time (p=0.03 or less, p= 0.04 or less, and p=0.01 or less). In contrast, plasma renin activities at every sampling time were significantly lower in patients than in controls (p= 0.04 or less). Plasma aldosterone and noradrenaline levels were not significantly different at every sampling time in the two groups. No significant differences in daily renal sodium excretion were found. However, urinary cyclic guanosine monophosphate excretion was significantly higher in patients than in controls (p<0.01). CONCLUSIONS: The initial abnormalities of sodium metabolism in cirrhosis might be characterized by blunted renal responsiveness to natriuretic peptides. The results of the study also provide indirect evidence that the impairment is mainly located at postreceptor levels of signal transduction pathway to the peptides, if the activation of antinatriuretic factors other than renin-angiotensin or sympathoadrenergic systems does not play a role.

Adult↗
PubMed2000

Ordering process of Cu3Pt from short-range order state studied by in-situ TEM observation

The state of short-range order (SRO) and the ordering process in Cu3Pt have been studied by the in-situ transmission electron microscope observation method. In order to detect weak diffraction-patterns and weak image-contrasts, an imaging plate system and/or digital-process of video-recorded signals were applied. It is confirmed that above the critical temperature for ordering, Tc, the alloy shows diffuse scattering in its electron diffraction pattern. The appearance of the diffuse scattering indicates that the "disordered" Cu3Pt (designated as A1) has an SRO-state in thermoequilibrium. Dark field images taken by using the diffuse scattering shows a fine dot-contrast, which indicates the presence of "microdomains". The dot-contrast is flickering at higher temperatures, but the rate of flickering decreases with falling temperature and finally stops before reaching Tc. On further decreasing temperature, some of the microdomains grow up to large domains of the long period superstructure (L12-s) phase. This indicates that the transformation to L12-s via SRO proceeds without a process of nucleation even though the transformation is of a first-order.

Journal Article↗
PubMed2000

Different cytokines are required for induction and maintenance of the Th2 type response in DBA/2 mice resistant to infection with Leishmania major.

Experimental cutaneous leishmaniasis is a useful model in studying the mechanism regulating immune responses between T helper type 1 (Th1) and Th2. Mice susceptible to Leishmania major infection such as BALB/c (H-2(d)) are associated with the induction of the disease-promoting Th2 response, while the resistant mice such as DBA/2 (H-2(d)) develop the protective Th1 response. To understand the induction mechanism of Th1 and Th2 responses, it is necessary to establish an immunization scheme by which the induction of each Th response can be easily and experimentally controlled. Adjuvants are known to enhance the immune responses through the combined effect of several factors: prolonged release of antigen, migration of cells, mitogenic effect and so forth. When the genetically resistant DBA/2 mice were immunized twice with soluble leishmanial antigen (SLA), emulsified in incomplete Freund's adjuvant (IFA) before L. major inoculation, these mice mounted a Th2 cell response and suffered from progressive infection. While IL-4 and IL-13 were upregulated early after the infection in both healer and non-healer groups of mice, IL-5 and IL-10 were upregulated only in non-healer mice. From these results, IL-5 and IL-10 appear to have an important role, at least in the early phases of the infection, rather than IL-4 and IL-13 in establishing the disease-promoting Th2 response in leishmaniasis. Further, IL-9 was found to be expressed in both BALB/c and DBA/2 mice immunized with IFA/SLA. This cytokine may support the establishment of a Th2 response in these mice. Therefore it is suggested that Th2 cytokines play different roles between priming and maintaining the Th2 immune response after the infection.

Animals↗
PubMed2000

Media selection for refolding of thermolysin by use of immobilized preparation.

Selection of the most effective medium for the correct refolding of thermolysin was performed. Thermolysin that had been denatured with 6 M guanidinium chloride at pH 2.0 could not be recovered to its activity larger than ca. 10% even when the denaturant was diluted with a conventional buffer solution. The amount of activity recovered by this method decreased with time. The recovered activity was ca. 20% at most where 1 M calcium chloride or 1.6 M calcium acetate was employed as the refolding medium instead of the conventional buffer solution. In this case also, the activity decreased with time. Not only the low recovered activity or yield, but also the elimination of the activity once recovered, was probably mainly due to the intermolecular interactions between protein molecules such as autolysis and aggregation. In order to exclude the influence of the intermolecular interactions and to select the effective media for the correct refolding of thermolysin, immobilized thermolysin was prepared using agarose gel. Employment of the immobilized preparation made it possible to quantitatively determine the refolding of thermolysin and results revealed that the salts of organic acid, such as potassium acetate and sodium acetate, were excellent media for refolding. The immobilization was confirmed to be available for the selection of protein refolding media and indispensable, especially in the case of proteases. Since these results were partly similar to those obtained in the case of subtilisin reported previously, results of both cases were compared.

Journal Article↗
PubMed2000

Enzymatic synthesis of L-[4-13C]aspartic acid.

An efficient procedure for the production of l-[4-13C]aspartic acid (4-13C-Asp) was investigated. In this procedure, phosphoenolpyruvate carboxylase originating from the methanol-assimilating microbe, Methylobacterium extorquens JCM 2805, was used for the production of labeled oxaloacetic acid from phosphoenolpyruvate (PEP) and NaH13CO3; the oxaloacetic acid was then converted to 4-13C-Asp with glutamic-oxaloacetic transaminase. In this reaction, with starting concentrations of 10 mM PEP, 10 mM NaH13CO3 and 15 mM L-glutamic acid (Glu), the yield was 70%. 4-13C-Asp and Glu in the final reaction mixture were separated by displacement chromatography. The yield of this process was 84%. The overall yield was 59%. The incorporation of 13C at the C-4 position of 4-13C-Asp was confirmed by NMR spectroscopy.

Journal Article↗
PubMed2000

Analysis of Helicobacter pylori vacA gene and serum antibodies to VacA in Japan.

Vacuolating cytotoxin, VacA, is one of the most important pathogenetic factors produced by Helicobacter pylori. However, it is not clear whether the diversity in disease outcome may be ascribed to variations in strain and/or to the host responses to virulence factors. In this study, we analyzed the vacA middle region sequence among 65 Japanese isolates to clarify the variation in strain and assayed antibody titer to VacA by ELISA using purified VacA to evaluate the host response to cytotoxin. The nucleotide sequence identities compared among Japanese isolates were 92.8 +/- 3.56%, and compared to 88.3 +/- 2.89% in tox+ strains reported in GenBank. Positive correlation was found between the antibody titers and the severity of atrophic change of the stomach. In Japan the nucleotide sequences of the vacA middle region were highly homologous and genetically closer to tox+ strains. Antibody titers and host response to cytotoxin may be associated with atrophy of the stomach.

Adult↗
PubMed2000

Use of an EEG-bispectral closed-loop delivery system for administering propofol.

Closed-loop control of propofol delivery was instituted in three patients who received a propofol infusion as part of: (Case 1) general "balanced" anesthesia, (Case 2) total intravenous anesthesia, and (Case 3) monitored anesthesia care. The bispectral index was the input variable used in a proportioned, integral and differential controller to determine the infusion rate of propofol required to maintain a stable level of hypnosis (Cases 1 and 2) or sedation (Case 3). This feedback control system provided intraoperative hemodynamic stability and a prompt recovery from the sedative-hypnotic effects of propofol.

Adjuvants, Anesthesia↗
PubMed2000

Lysosomal cathepsin B plays an important role in antigen processing, while cathepsin D is involved in degradation of the invariant chain inovalbumin-immunized mice.

We previously reported that CA074, a specific inhibitor of cathepsin B, modulates specific immune responses from the T helper 2 (Th2) type to Th1 type in BALB/c mice infected with Leishmania major. In the present study, we found that a similar type of immune deviation was also induced in mice immunized with ovalbumin (OVA). However, treatment of mice with pepstatin A, a specific cathepsin D inhibitor, suppressed the OVA-specific proliferation of lymphocytes and blocked the development of both Th1 and Th2 cellular responses. These inhibitors did not appear to have any direct influence in vitro on functions of naive lymphocytes. OVA antigen (47 000 MW) was digested mainly into 40 000 MW protein in vitro by lysosomal proteases from naive BALB/c mice, and its digestion was markedly inhibited by the addition of CA074, but not by addition of pepstatin A, during incubation. However, pepstatin A strongly suppressed the degradation of the major histocompatibility complex class II-associated invariant chain (Ii) molecule in vivo and in vitro. Thus, cathepsin B appears to process antigens directed to preferential activation of Th2 cells, while cathepsin D may be responsible for the degradation of Ii, the processing of which is essential in initiating the antigen-specific activation of Th1 and Th2 CD4+ T cells. These lysosomal proteases may have different functions in regulating immune responses.

Animals↗
PubMed2000

Gene gun-mediated delivery of an interleukin-12 expression plasmid protects against infections with the intracellular protozoan parasites Leishmania major and Trypanosoma cruzi in mice.

An interleukin-12 (IL-12) expression plasmid was transferred, using a gene gun, to mice infected with Leishmania major or Trypanosoma cruzi. Transfer of the IL-12 gene to susceptible BALB/c mice resulted in regression of lesion size and reduced the number of parasites in draining lymph nodes (LN) at the site of L. major infection. Coincident with these protective effects, the T-helper type (Th) response shifted towards Th1, as evaluated by cytokine production in vitro and L. major-specific antibody responses. Protective effects of the IL-12 gene were also observed in T. cruzi infection. Treatment of BALB/c mice infected with T. cruzi enhanced the production of interferon-gamma (IFN-gamma) by spleen cells, while suppressed production of interleukin-10 (IL-10) compared with control mice. Administration of anti-CD4 or anti-CD8 monoclonal antibody (mAb) abolished the protective immunity against T. cruzi infection, and treatment with the IL-12 gene could not restore the resistance in these mice. Mice depleted of natural killer (NK) cells with anti-asialo GM1 also became susceptible to infection, while the resistance was restored when these mice were treated with the IL-12 gene. Thus, target cells for the treatment appear to be CD4+ and CD8+ T cells, which are ordinarily activated by NK cells. These results suggest that the transfer of cytokine genes using a gene gun is an effective method for investigating the roles of cytokines and gene therapy in infectious diseases.

Animals↗
PubMed2000

Peripheral or central administration of motilin suppresses LH release in female rats: a novel role for motilin.

Motilin is secreted in a clear episodic pattern during fasting or during the interdigestive phase, but feeding promptly stops this secretory pattern, and plasma concentrations of motilin decrease. We have previously determined that fasting markedly suppresses pulsatile luteinizing hormone (LH) secretion in female rats in the presence of oestrogen. In the present study, we wished to learn if motilin may mediate the fasting-induced suppression of LH secretion by determining the effects of motilin administration on LH release and on food intake. Intravenous (i.v.) injection of motilin (37 nmol/rat) suppressed LH release and significantly decreased mean LH concentrations both in ovariectomized (OVX) and oestradiol-implanted ovariectomized (OVX+E2) rats. Food intake was significantly increased by i.v. motilin injection in OVX rats, but not in OVX+E2 rats. It is likely that motilin inhibits LH release via inhibition of the gonadotrophin-releasing hormone (GnRH)-releasing mechanism at the hypothalamic level, because motilin (3.7 nmol/rat) also suppressed LH secretion when centrally administered, and because LH release in i.v. motilin-treated rats increased in response to exogenous GnRH. These results suggest that motilin may be a peripheral signal for the suppression of LH secretion through central sensors.

Animals↗
PubMed2000

Myotonic dystrophy associated with 47 XYY syndrome.

A case of myotonic dystrophy with 47 XYY presented with tall stature and mental retardation. The patient was a 37-year-old male. In addition to grip myotonia and percussion myotonia, severe weakness and atrophy were noted in the face and the neck muscles and in the distal muscles of the four limbs. He also had diabetes mellitus, cataracts and sexual behavior abnormalities. He was found to be 47 XYY from chromosomal examinations. The combination of 47 XYY syndrome and myotonic dystrophy has not been reported previously.

Adult↗
PubMed2000

Ultrastructural localisation and size distribution of collagen fibrils in Glisson's sheath of rat liver: implications for mechanical environment and possible producing cells.

The ultrastructure and size distributions of collagen fibrils in Glisson's sheath were investigated in the rat liver to analyse the mechanical environment around the fibrils and their possible cells of origin. Glisson's sheath was found to contain 2 populations of collagen fibrils with different diameters and distinct localisations, namely fibroblast-associated and bile epithelium-associated. Fibroblast-associated collagen was composed of fibrils arranged in bundles and constituted the majority of the collagen in Glisson's sheath. Bile epithelium-associated collagen was represented by small dispersed groups of fibrils just beneath the basement membrane of the bile duct. The basement membrane of the bile duct was frequently reduplicated into a few or as many as 10 layers of laminae densae, with scattered collagen fibrils between these laminae. The diameters of the fibrils of both groups of collagen increased in relation to the calibre of the bile duct, whereas at any given place in Glisson's sheath bile epithelium-associated collagen fibrils had a smaller diameter compared with those of the fibroblast-associated fibrils. The increment in fibril diameter along the bile duct is considered to be correlated with the increase in mechanical stress acting on Glisson's sheath. The difference in diameter between the 2 populations as well as the incorporation of fibrils between the laminae densae of the basement membrane of the bile duct supports the view that the bile epithelium-associated collagen is produced by the epithelial cells of the bile duct, thus having a different origin from that of fibroblast-associated collagen. These findings provide the first evidence that the epithelial cells of the interlobular bile duct produce fibril-forming collagen. Furthermore, it is suggested that cholestasis stimulates the epithelial cells of interlobular bile duct to increased synthesis of fibril-forming collagen that is also produced by these cells under physiological conditions.

Animals↗
PubMed2000

Cloning of rat nephrin: expression in developing glomeruli and in proteinuric states.

BACKGROUND: Nephrin is identified as a product of the gene mutated in a patient with congenital nephrotic syndrome of the Finnish type. However, its precise localization and function are not yet fully clarified. METHODS: To clone the rat homologue of nephrin, polymerase chain reaction (PCR) was employed. To elucidate the localization and expression of nephrin, immunohistological analysis with a specific antirat nephrin antibody, reverse transcription-PCR, and RNase protection assay were performed. RESULTS: Amino acid sequences of rat and human nephrin are highly homologous (82.2% identity). The domain structure of nephrin is also highly conserved between rats and humans. The rat nephrin was detected only in kidney glomeruli along glomerular capillary walls, and its localization was always identical to that of the anti-slit diaphragm monoclonal antibody (mAb) 5-1-6-recognized antigen in normal matured and fetal rat glomeruli and in the glomeruli of proteinuric states. The nephrin staining pattern was clearly distinguished from that of zonula occludens-1 (ZO-1), alpha3-integrin, or podocalyxin. mRNA expression for nephrin was first detected in the fetal rat kidneys at 18.5 embryonic days. Nephrin mRNA expression decreased just after injection of mAb 5-1-6 (47.4%) or puromycin aminonucleoside (51.2%), and the staining pattern of nephrin shifted from a linear to a granular pattern in both proteinuric states. CONCLUSIONS: Nephrin is localized in slit diaphragm in the matured glomeruli and is identical with mAb 5-1-6 antigen. Nephrin is involved in the development of proteinuria not only in mAb 5-1-6 nephropathy, but also in puromycin aminonucleoside nephropathy.

Amino Acid Sequence↗
PubMed2000

A multicenter trial of mizoribine compared with placebo in children with frequently relapsing nephrotic syndrome.

BACKGROUND: The use of corticosteroids or cytotoxic/immunosuppressive agents such as cyclophosphamide, chlorambucil, and cyclosporine for the treatment of frequently relapsing nephrotic syndrome (FRNS) is limited because of their adverse effects. This study was conducted to evaluate the efficacy and safety of mizoribine, a relatively new immunosuppressive drug developed in Japan, in children with FRNS. METHODS: A double-blind, placebo-controlled, multicenter trial was carried out in children, from 2 to 19 years old, with FRNS. At relapse, patients were treated with prednisolone. According to a dynamic allocation, mizoribine or a placebo was concurrently administered to each patient. Prednisolone was gradually tapered and discontinued within 12 weeks. The test drug was maintained for 48 weeks. The primary end point was the relapse rate (the total number of relapses/the total treatment days for all patients). Analyses were performed according to the intention-to-treat principle. RESULTS: The primary analysis was conducted on 99 mizoribine- and 98 placebo-treated patients. The relapse rate was lower in the mizoribine group than in the placebo group (0.0055 vs. 0.0067; ratio 0.81, 95% CI, 0.61 to 1.05, P = 0.12). The hazard ratio of the cumulative remission rate between the two groups was 0.79 (95% CI, 0. 57 to 1.08). In the subgroups consisting of patients 10 years old or younger, the relapse rate ratio between the mizoribine subgroup (54 patients) and the placebo subgroup (57 patients) was 0.66 (95% CI, 0. 44 to 0.94, P = 0.017). The hazard ratio of the cumulative remission rate between the two subgroups was 0.56 (95% CI, 0.37 to 0.85, P = 0. 007). Hyperuricemia was the most common adverse event with mizoribine (16%), but was transient. CONCLUSIONS: Compared with the placebo, mizoribine significantly decreased the relapse rate and prolonged the remission period in the subgroup consisting of patients 10 years old or younger. This drug may be useful in young children with FRNS who generally relapse more frequently than older children.

Adolescent↗
PubMed2000

Activation of natural killer T cells by alpha-galactosylceramide in the presence of CD1d provides protection against colitis in mice.

BACKGROUND & AIMS: CD1d is a major histocompatibility complex class I-like molecule that presents glycolipid antigens to a subset of natural killer (NK)1.1(+) T cells. These NK T cells exhibit important immunoregulatory functions in several autoimmune disease models. METHODS: To investigate whether CD1d and NK T cells have a similar role in intestinal inflammation, the effects of the glycolipid, alpha-galactosylceramide (alpha-GalCer), on dextran sodium sulfate (DSS)-induced colitis were examined. Wild-type (WT), CD1d(-/-), and RAG(-/-) mice were examined for their response to either alpha-GalCer or the control analogue, alpha-mannosylceramide (alpha-ManCer). RESULTS: WT mice, but not CD1d(-/-) and RAG(-/-) mice, receiving alpha-GalCer had a significant improvement in DSS-induced colitis based on body weight, bleeding, diarrhea, and survival when compared with those receiving alpha-ManCer. Elimination of NK T cells through antibody-mediated depletion resulted in a reduction of the effect of alpha-GalCer. Furthermore, adoptive transfer of NK T cells preactivated by alpha-GalCer, but not alpha-ManCer, resulted in diminished colitis. Using a fluorescent-labeled analogue of alpha-GalCer, confocal microscopy localized alpha-GalCer to the colonic surface epithelium of WT but not CD1d(-/-) mice, indicating alpha-GalCer binds CD1d in the intestinal epithelium and may be functionally active at this site. CONCLUSIONS: These results show an important functional role for NK T cells, activated by alpha-GalCer in a CD1d-restricted manner, in regulating intestinal inflammation.

Animals↗
PubMed2000

Osteonecrosis of the patella in patients with nontraumatic osteonecrosis of the femoral head: MRI findings in 60 patients.

We examined both knees in 60 patients with nontraumatic osteonecrosis of the femoral head with three-dimensional MRI. We found osteonecrosis of the patella in 9 patients (10 knees) and osteonecrosis of the femoral or tibial condyles/metaphyses in 35 patients (61 knees). In the patella, the necrosis was located in the proximal half and tended to develop in patients with other necrotic lesions in the knee.

Adolescent↗